<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta name="author" content="VectorX">
    <meta name="keywords" content="after">
    <meta name="description" content="::after伪元素选择器">
    <title>after</title>
    <style>
        .box1 {
            border: 10px olive solid;
            /* overflow: hidden; */
        }

        .box2 {
            width: 200px;
            height: 200px;
            background-color: red;
            float: left;
        }

        .box1::after {
            content: '';
            clear: both;
            display: block;
        }
    </style>
</head>

<body>
    <div class="box1">
        <div class="box2"></div>
    </div>
</body>

</html>